Peripheral neuropathy plays a major role in the development of diabetic foot ulceration (DFU) because of the pain insensitivity that allows prolonged tissue injury till a chronic wound has been developed. However, recent studies by our unit and elsewhere indicate that the neuropathy-associated lack of locally secreted neuropeptides by the C-nociceptive fibers impair wound healing and this may be of the major reasons that lead to the development of chronic DFU that may necessitate amputation. In the present application we plan to identify the mechanisms through which, the neuropathy-associated lack of neuropeptides and chronic inflammation lead to wound healing failure. Our primary hypothesis is that the lack of neuropeptides in association with the diabetes-induced pro-inflammatory state lead to increased expression and activity of protein tyrosine phosphatase 1B (PTP1B) causing reduced growth factor signaling, reduced fibroblast function and impaired wound healing. In addition, we hypothesize that diabetes-induced PTP1B expression and the neuropathy-related neuropeptide deficiency leads to impaired mast cell function results in deficient secretion of various cytokines and angiogenic factors that reduces angiogenesis and further impairs wound healing. We finally hypothesize that inhibition of PTP1B and mast cell stabilization in diabetic animal models will improve wound healing and lead to the development of new therapeutic approaches. In order to explore our hypothesis, we propose a prospective cohort follow up study in diabetic patients to study the relationship between the severity of neuropathy and neuropeptides expression to PTP1B forefoot and forearm skin expression/activity and mast cell number and activation. We will also examine the association between PTP1B, mast cells and changes in cytokines and growth factors to wound healing impairment. We also propose animal studies that will examine whether interventions that affect these mechanisms can affect the progress of wound healing and can lead to the development of new therapeutic approaches. The proposal has three specific aims: 1.) To explore the hypothesis that the deficiency of neuropeptides in association with the diabetes-induced pro-inflammatory state lead to increased PTP1B expression/activity and mast cell dysfunction are associated with impaired wound healing; 2.) To investigate whether PTP1B inhibition can improve wound healing in diabetes; 3.) To examine whether neuropeptide deficiency causes mast cell dysfunction and contributes to wound healing impairment in diabetes. The application will encompass the collaboration of investigators from the Joslin-Beth Israel Deaconess Foot Center, Vascular Surgery and Endocrinology and the Molecular Immunopharmacology and Drug Discovery Lab at Tufts Medical Center. The collaboration among the various disciplines creates very strong synergy and will lead to novel and clinically useful data and has the potential to create a paradigm shift in the current thinking, lead to seminal discoveries that can be translated to new therapeutic approaches.